It is known to use vehicle control systems to assist drivers in certain aspects of driving. For example, cruise control systems act to automatically maintain the speed of a vehicle at a speed set by a driver. Also, parking assistance systems can either assist a driver when parking a vehicle (for example, by controlling the direction of the vehicle when parking while the driver controls the speed), or can park a vehicle automatically without further driver input beyond activating the system.
To safely park a vehicle, parking assistance systems often include means for sensing the positions of vehicles, structures or other objects relative to the vehicle to be parked. The parking assistance systems record the positions of these objects, and then control the vehicle in such a way that the objects are avoided, such that the vehicle can be safely parked.
Also known, and increasing in popularity in several countries, are electric vehicles. Electric vehicles have been used in niche roles (milk delivery vehicles, golf carts, etc.) for some time, but quite recently electric vehicles have begun to replace ordinary vehicles for everyday road use.
In hybrid electric vehicles a portion of the output from a further vehicle mounted engine, typically a petrol or diesel engine, is used to charge a vehicle mounted battery pack. The vehicle mounted battery pack can then be used to provide movement power to the vehicle in addition to, or alternatively to, the further vehicle mounted engine. Hybrid electric vehicles therefore typically do not require an external power source to charge the vehicle mounted battery pack, though some hybrid electric vehicles are configured such that the vehicle mounted battery pack can be charged using an external power source if one is available.
Fully electric vehicles, which are vehicles which use an electric motor as their primary or only source of motive power, typically require external power sources in order to charge the vehicle mounted battery packs which power the engines.
Electric vehicles which can use external power sources to charge the battery packs are usually connected to the external power source using a conductive charging system based on a standard or three phase power cable. The power cable connects to an external power source, such as a connection point to a national power network, a stand alone power source or any other power source suitable for charging vehicle mounted battery packs, and also connects to the vehicle. Power can then be routed from the external power source to the vehicle, charging the vehicle.
Power cables can be a source of obstructions, potentially impeding the movement of vehicle users or other pedestrians. Also, vehicle users may forget to connect the power cable to the vehicle, or to the external power source, leading to the vehicle mounted battery packs failing to charge and potentially stranding the user with no motive power. If a power cable is connected to the external power source and the vehicle, but not disconnected before the vehicle moves away, this could potentially cause serious damage to the vehicle, the connection to the external power source and surrounding structures, vehicles and other objects. Conductive charging systems require a conductive connection to be made between the vehicle and the external power source, which could potentially lead to users being injured by electric shocks from the elements forming the conductive connection.
To obviate the issues surrounding power cables, prototype systems for charging electric vehicles using inductive charging systems are being developed. Inductive charging systems require no physical connection between an external power source and a vehicle to be charged. Instead, an electromagnetic field is used to transfer energy between two inductive charging points, which typically use induction coils to transfer the energy. An electromagnetic field is generated by a fixed inductive charging point connected to the external power source, and then the power from the field is received by a mobile inductive charging point on the vehicle to be charged and converted back into electrical energy.
There is no physical connection between the inductive charging points; the electromagnetic field propagates through the gap between the charging points. Therefore, there is no power cable to impede the movement of vehicle users or other pedestrians. As there is no power cable, it cannot be left connected between the vehicle and the external power source. Further, as there is no requirement for any physical connection between the vehicle and the external power source, it is possible for inductive charging systems to be configured to activate automatically, thereby reducing the possibility of the vehicle failing to charge. The removal of the physical connection also means that all of the elements carrying electrical power can be shielded behind insulating material, reducing the risk of a user suffering an electrical shock.
The transfer efficiency of inductive charging systems is a function of the separation between the inductive charging points. Therefore, in order to maximize the efficiency of the system it is advisable to position the inductive charging points of the vehicle and the external power source as close to one another as possible. Current prototype systems are configured such that the driver is responsible for aligning the fixed and mobile inductive charging points such that a connection between the two can be established. However, this can be a time consuming task for the driver, and it can be difficult for the driver to reliably position the vehicle in the optimal charging position for power transfer.
Certain examples described herein aim to avoid the above problems by providing assistance to the driver in the positioning of the vehicle. A parking assistance system may be configured to automatically detect the location of a fixed inductive charging point. When the location of a fixed inductive charging point has been determined, the parking assistance system is further configured to automatically position the vehicle relative to the detected location of the fixed inductive charging point such that the fixed and mobile inductive charging points are substantially aligned. In this way, an optimal connection between the fixed and mobile inductive charging points can be established. The system can either position the vehicle without driver input, or can assist the driver in positioning the vehicle. The parking assistance system can position the vehicle relative to the fixed inductive charging point faster and more reliably than the driver would be able to do without assistance from the parking assistance system. An optimal connection between the fixed and mobile inductive charging points helps to minimize the charging time, the energy lost during charging, and the cost of charging.